Abstract:
Serious medical conditions due to sudden outbreaks of Tetraponera rufonigra and
increase of its stings in urban localities were reported recently in Sri Lanka. Control
methods appropriate for suppressing T. rufonigra workers in such situations were
investigated using kerosene or citronella oil in the laboratory. Toxicity tests were
conducted with appropriate control experiments and in three replicates, by applying
10 μl, 12 μl, 14 μl, 16 μl, 18 μl and 20 μl of citronella oil on dorsal prothorax of each
of the acclimatized ten workers used in each treatment. Number of dead ants
observed with each treatment was recorded after 10 minutes of each application.
Probit analysis performed with the percentage mortality of workers resulted 6.38
mg/mg body weight of ant of citronella oil as LD99 of the workers.
For field simulating experiments, citronella oil containing (100%) sprayer bottle and
a common hand sprayer were bought and spray volume of each sprayer was
calculated. Increasing volumes 0.6 ml, 1.2 ml, 1.8 ml, 2.4 ml and 3.0 ml of kerosene
or 0.64 ml, 1.28 ml, 2.56 ml, 3.84 ml and 5.18 ml citronella oil based on the
calculated spray volumes, were applied separately to ten acclimatized workers in a
plastic bottle in three replicates; time period until ten worker ants died since spraying
was recorded for each treatment. Appropriate control set up was maintained for each
treatment. Spraying of 3.0 ml of kerosene or 5.2 ml of citronella oil, as minimum
volumes, is recommended for the temporary suppression of ten worker ants.
